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<html lang="en">

<head>
   <meta charset="UTF-8">
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Document</title>
</head>

<body>

</body>
<script>


   let a = {
      name: 'Julia',
      age: 20
   }

   function change(o) {
      o.age = 24;
      o = {
         name: 'Kath',
         age: 30
      }
      return o;
   }
   let b = change(a);
   console.log(b.age);
   console.log(a.age);
</script>

</html>